The present invention relates to a semiconductor device having a circuit composed of field effect transistors (referred below to as FET), and a method of manufacturing the same. In addition, FET referred to in the specification of the present application indicates general elements, in which the basic principle of FET is embodied as an element, and includes MIS FET, MOS FET making use of oxides for insulator films, and thin film transistors making use of semiconductor thin films. The invention specifically relates to an electronic equipment, on which a semiconductor device having a Light Emitting Diode is loaded as a part.
In addition, a semiconductor device referred to in the specification of the present application indicates devices in general making use of semiconductor characteristics to be able to function, and electro-optic devices, light emitting devices, semiconductor circuits, and electronic equipments are all indicated as semiconductor devices.
Also, semiconductor devices include all modules, in which connectors, for example, FPC (Flexible printed circuit), or TAB (Tape Automated Bonding) tape, or TCP (Tape Carrier Package), are mounted on a light emitting device, modules, in which a printed circuit board is provided on a tip end of TAB tape, or TCP, or modules, in which an IC (integrated circuit) is packaged directly on a light emitting diode by means of COG (Chip On Glass).
In recent years, light emitting devices having an EL element as a self-light emitting element have been actively studied, and in particular, attention has been paid to light emitting devices making use of organic materials as an EL material. Such a light emitting device is called an EL Display, or a Light Emitting Diode. Note that, a light emitting device referred to in the specification of the present application indicates an graphic display device, light emitting device, or a light source (includes a lighting device).
In addition, EL elements comprise a layer (referred below to as EL layer) containing an organic chemical compound, in which light emitting (Electro Luminescence) generated upon application of an electric field is obtained, anode, and cathode. While light emitting in organic chemical compounds includes emission (fluorescence) generated when returned to a ground state from a singlet excitation state, and emission (phosphorescence) generated when returned to a ground state from a triplet excitation state, light emitting devices fabricated by a deposition apparatus and a deposition method, according to the invention, are applicable to the cases where either emission is used.
light emitting devices has a feature in that there is caused no problem in angle of visibility because they are of self-light emitting type unlike liquid crystal displays. That is, the devices are more suitable than liquid crystal displays when used as displays in the open air, and use thereof has been proposed in various configurations.
While an EL element is configured such that an EL layer is interposed between a pair of electrodes, the EL layer generally has a laminated structure. Typically, a laminated structure “hole transport layer/light emitting layer/electron transport layer” is listed. This structure is very high in light emitting efficiency and adopted by almost all light emitting devices, which are presently being studied and developed.
Also, light emitting elements formed by a cathode, an EL layer, and an anode are called EL elements, and include two types, that is, a system (simple matrix system), in which an EL layer is formed between two kinds of stripe-shaped electrodes provided perpendicular to each other, and a system (active matrix, system), in which an EL layer is formed between a pixel electrode connected to TFT and arranged in a matrix configuration and an opposed electrode. However, it is believed that in the case where pixels are increased in density, the active matrix system, in which switches are provided every pixel (or one dot), is advantageous.
Also, active matrix type light emitting devices have been structured, in which an electrode electrically connected to a TFT on a substrate is formed as an anode, an organic compound layer is formed on the anode, a light emitting element with a cathode formed on the organic compound layer is provided, and light generated on the organic compound layer is taken out toward a TFT from the anode being a transparent electrode.
Hereupon, according to the invention, active matrix type light emitting devices are fabricated having a light emitting element of a structure (referred below to as upper-surface outgoing structure), in which a first electrode is formed as an anode, a layer containing an organic compound layer is formed on the anode, and a cathode composed of a second electrode for transmission of emission is formed on the layer containing an organic compound layer. Alternatively, active matrix type light emitting devises are fabricated having a light emitting element of a structure, in which a first electrode is formed as a cathode, a layer containing an organic compound layer is formed on the cathode, and an anode composed of a second electrode for transmission of emission is formed on the layer containing an organic compound layer.
Also, all the light generated on the layer containing an organic compound layer is not taken out toward an observer (user) but light is emitted, for example, laterally (direction in parallel to the substrate surface), and as a result, the light emitted laterally is not taken out and so constitutes a loss. Hereupon, the invention has its object to provide a light emitting device structured to increase a quantity of light taken out in a certain direction, and a method of fabricating the same.
Also, in a light emitting element having an organic compound, let consider a path, along which electrons and holes injected from electrodes are converted into photons to be finally taken out of the element. Only a certain ratio of electric current flowing through an external circuit can contribute to carrier combination as an electron-hole pair, and a portion of the electron-hole pair as recombined is consumed for generation of light emitting molecular excitons. The generated excitons are converted into photons in a ratio prescribed by fluorescence quantum efficiency, and the remainder is deactivated in various paths to make, for example, thermal deactivation and emission of infrared light. Accordingly, when such light emitting element is driven to make emission, Joule heat is generated to incur decomposition and crystallization of an organic compound layer, thus causing deterioration of the light emitting element.